In recent years, carbon nanotubes (hereinafter, also referred to as “CNTs”) have been attracting attention as materials having excellent electrical conductivity, thermal conductivity, and mechanical characteristics.
However, CNTs are fine tubular structures having nanometer-size diameters, which makes handling and processing of individual CNTs difficult. In consideration of this, it has for example been proposed that a plurality of CNTs may be assembled into a fibrous shape to form a carbon nanotube fiber (hereinafter, also referred to as a “CNT fiber”), and this CNT fiber may be used individually or may be used as part of a yarn (for example, refer to PTL 1 and 2). Furthermore, there is much interest in using such CNT fibers as fibrous materials having excellent electrical conductivity, thermal conductivity, and mechanical characteristics.